This Program Project includes six research projects and one intervention project from the University of Wisconsin Waisman Center for Mental Retardation and related aspects of Human Development. These projects represent a cooperative effort to investigate the developmental processes that characterize high-risk and retarded children and examine the usefulness of intervention procedures with high-risk children. The research projects deal with infants' neurological development, attention, and language development, as well as cognitive processes such as information input, rehearsal, and organizing factors, as they are related to the intellectual functioning of preschool and older children. The children at high-risk for mental retardation which will be studied include a population from St. Mary's Hospital Regional Neonatal Intensive Care Unit and an outpatient population of PKU children from the Diagnostic and Treatment Unit of the Waisman Center. The objectives of the Project are to 1) identify and systematically investigate processes important for the development of intellectual competence, 2) identify differences in the functioning of these processes and specify their course of development in high-risk, retarded and normal children, 3) determine the value of process difference information in predicting the later intellectual competence of high-risk children, 4) examine the effectiveness of home and preschool intervention programs with high-risk children, 5) investigate the value of process information in predicting and assessing the outcome of intervention procedures, and 6) provide basic information about the processes underlying intellectual competence that will be of value in developing remediation and/or compensatory procedures for those performing at a subaverage intellectual level.